A study of the phase equilibrium for quinary system Li+, Na+, K+//CO32-, Cl--H2O at 298.15 K

Zabuye Saline Lake, Tibet, P. R. China, is unrivalled in the world for its high concentration of chloride, sulfate, carbonate and borate of lithium, sodium and potassium. In accordance with the composition of the brine, the phase equilibrium of quinary system Li+, Na+, K+//CO32-, Cl--H2O at 298. 15 K were studied by isothermal method, from which the phase diagram (stereo-diagram and projected-diagram which were saturated with Li2CO3) were drawn. The phase diagram of this quinary system consists of seven crystallization fields, thirteen univariant curves and four invariant points. Seven crystallization fields correspond to six single-salt crystallization fields and one complex salt crystallization, that are LiCl . H2O, NaCl, K2Cl2, Li2CO3, K2CO3 . 3/2H(2)O, Na2CO3 . 10H(2)O and complex salt NaKCO3 . 6H(2)O. The crystallization region of trona (Na2CO3 . NaHCO3 . 2H(2)O) or solid solution is not found in this quinary system. The composition of equilibrium solid phase for four invariant points (K-1, K-2, K-3, K-4) is as follows: Li2CO3+NaKCO3 . 6H(2)O+Na2CO3 . 10H(2)O+KCl for K-1, Li2CO3+NaKCO3 . 6H(2)O+K2CO3 . 3/2H(2)O+KCl for K-2, Li2CO3+NaCl+KCl+LiCl . H2O for K-3, Li2CO3+NaCl+Na2CO3 . 10H(2)O+KCl for K-4, respectively.